Gas turbines are widely used in commercial operations for power generation. Gas turbines generally include a compressor at the front, one or more combustors around the middle, and a turbine at the rear. The compressor progressively compresses a working fluid and discharges the compressed working fluid to the combustors. The combustors mix the working fluid with fuel and ignite the mixture to produce combustion gases having a high temperature, pressure, and velocity. The combustion gases exit the combustors and flow to the turbine where they expand to produce work.
The combustion gases include various amounts of undesirable emissions, such as unburned hydrocarbons and various nitrogen oxide (NOx) compounds. The amount of unburned hydrocarbons and NOx compounds present in the combustion gases depends on the efficiency and temperature of the combustion. Specifically, incomplete or inefficient combustion of the fuel results in increased hydrocarbon emissions. Similarly, increased combustion temperatures result in increased NOx emissions.
Various efforts have been made to reduce the amount of hydrocarbon and NOx emissions by improving the combustion efficiency. For example, U.S. Pat. No. 5,259,184, which is incorporated here in its entirety for all purposes, describes a gas turbine burner that premixes the fuel and working fluid prior to combustion. The burner includes an annular swirler that imparts a swirling motion to the working fluid, and the swirling working fluid mixes with injected fuel to produce a more uniform, leaner fuel mixture for combustion. The more uniform, leaner fuel mixture increases combustion efficiency and reduces combustion temperature, thereby reducing hydrocarbon and NOx emissions.
U.S. Pat. No. 6,438,961, which is incorporated here in its entirety for all purposes, describes an improved gas turbine burner that mixes the fuel and working fluid prior to combustion. The burner includes turning vanes with built-in fuel passages. The turning vanes impart swirl to both the working fluid and the fuel to produce more uniform mixing of the fuel and working fluid prior to combustion.
The need exists for improved premixing of the fuel and working fluid prior to combustion to further improve combustion efficiency and reduce undesirable emissions.